LED Quantum Well Segmentation for Leakage Reduction
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Solution Overview
Problem
Current light emitting diodes (LEDs) face challenges in enhancing light extraction, active layer structure, current diffusion, and electrode structure to improve brightness and performance, particularly due to surface roughness of quantum well layers leading to leakage current and reduced crystal properties.
Innovation Solution
A light emitting device with a multiple quantum well structure, comprising alternately stacked sub-barrier and sub-quantum well layers formed through metal organic chemical vapor deposition, where the sub-quantum well layers have an increasing indium ratio, reducing surface roughness and leakage current, and improving crystal quality and light emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional quantum well layers are used in LED structure, then manufacturing process is simple, but surface roughness increases leading to leakage current and reduced crystal properties
Solution Approach 1:
The quantum well layer is segmented into multiple sub-quantum well layers (first, second, third sub-quantum well layers) with different indium compositions. This segmentation allows each sub-layer to contribute differently to the overall structure, reducing surface roughness while maintaining quantum well functionality. The segmented structure prevents the formation of large misfit dislocations that cause surface roughness in conventional single-layer quantum wells.
Solution Approach 2:
Different sub-quantum well layers are assigned different indium compositions (first sub-quantum well layer has higher indium content, second has intermediate, third has lower indium content). This local quality variation optimizes each layer's contribution: higher indium content layers provide better band alignment and reduce leakage, while lower indium content layers maintain crystal stability and reduce roughness. The gradient composition approach resolves the contradiction between reliability and structural simplicity.
2Use of energy by moving object
If indium ratio in quantum well layer is increased to improve light emitting efficiency, then recombination probability increases, but surface roughness increases causing leakage current
Solution Approach 1:
The indium composition parameter is varied across different sub-quantum well layers rather than being uniform. The first sub-quantum well layer has the highest indium ratio for maximum light emitting efficiency, the second has intermediate ratio, and the third has the lowest ratio. This parameter gradient allows the structure to achieve high overall efficiency while the lower indium content layers prevent excessive surface roughness and leakage current.
Solution Approach 2:
The quantum well structure is formed as a composite of multiple sub-layers with different indium-gallium-nitride compositions. This composite structure combines the advantages of high-indium layers (high efficiency) with low-indium layers (low roughness and leakage), achieving a balance that neither uniform composition could provide alone.
3Productivity
If conventional single-layer quantum well structure is used, then manufacturing is simpler, but light extraction and current diffusion are insufficient
Solution Approach 1:
The active layer's quantum well is divided into multiple sub-layers with graded indium composition. This segmentation improves light extraction by creating multiple interfaces with different refractive indices and enhances current diffusion through the gradient composition profile. The segmented structure achieves superior performance compared to single-layer wells while maintaining a systematic manufacturing approach.
Solution Approach 2:
The invention transitions from a single-layer quantum well (one-dimensional composition) to a multi-layer quantum well structure (multi-dimensional composition gradient). This dimensional change in composition space allows simultaneous optimization of multiple properties: light extraction efficiency, current diffusion, and crystal quality, which cannot be achieved with a single uniform composition layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The novel structure enhances light emitting efficiency by increasing recombination probability and reducing leakage current, resulting in improved crystal properties and enhanced brightness and performance of the LED.
Implementation Method 1
at least one barrier layer and at least one quantum well layer which are alternately stacked on the first conductive semiconductor layer and wherein the quantum well layer includes a plurality of sub-barrier layers, which are divided into first to nth sub-barrier layers sequentially stacked from the first sub-barrier layer, and a plurality of sub-quantum well layers, which are divided into first to nth sub-quantum well layers sequentially stacked from the first sub-quantum well layer
Implementation Method 2
The novel structure enhances light emitting efficiency by increasing recombination probability and reducing leakage current, resulting in improved crystal properties and enhanced brightness and performance of the LED
Data Source
AI summary
A light emitting device may include a first conductive semiconductor layer, an active layer adjacent to the first conductive semiconductor layer and a second conductive semiconductor layer adjacent to the active layer. The active layer may include a first quantum well layer, a second quantum well layer and a barrier layer between the first quantum well layer and the second quantum well layer. The first quantum well layer may include a first plurality of sub-barrier layers and a first plurality of sub-quantum well layers, and the second quantum well layer may include a second plurality of sub-barrier layers and a second plurality of sub-quantum well layers. A bandgap of the first quantum well layer may be different than a bandgap of the second quantum well layer.